DESCRIPTION: (Applicant's Description) Ras is the product of the proto-oncogene ras and is a key element in multiple signal transduction pathways involved in transmitting pro-proliferative signals to the cell from external growth factors and cytokines. The ras gene is mutated in a significant number of human cancers resulting in a constitutively active Ras protein that clearly plays an important role in the pathogenesis of the malignant phenotype. We have found that Ras is also activated in several cancers in the absence of an activating mutation in the ras gene; in these cases, Ras appears to be activated by mutation or overexpression of a growth factor receptor that signals via Ras activation or by a decrease in RasGTPase activitiy. A large number of Ras inhibitors are currently under development by the pharmaceutical industry and these agents have shown great promise in inhibiting growth of animal tumors driven by Ras activation; these drugs are not effective in tumors initiated by other oncogenes. At least one of these agents will enter Phase I Clinical Trials later this year. To measure the activation state of Ras in human cancers, we developed a method that does not rely on radioactively-labelling cells and measures absolute amounts of GTP and GDP bound to Ras. All steps of this procedure can be automated and in this grant application we propose to develop an instrument for that purpose. This instrument can be used in subsequent Phase II and III Clinical Trials of the Ras inhibitors and ultimately in clinical practice. It will allow clinicians to decide whether a particular patient is a candidate for a Ras inhibitor based on the activation state of Ras in the patient's tumor and it may also be used to monitor the effectiveness of the treatment. As more data become available, assessing the degree of Ras activation in a tumor may also be of prognostic value.